But environmentalists,
climate experts and others have pointed out that the critical warning from 13 federal agencies will be softened by the country's post-Thanksgiving haze and Black Friday shopping rush.

A Lake Worth lifeguard wearing a protective mask asks a surfer to exit the ocean as Palm Beach County officials announced that all county beaches are closed due to red tide affecting coastal areas on October 4, 2018 in Lake Worth, Florida. Joe Raedle / Getty Images

The same
red tide choking Florida's Gulf coast has spread to waters off Miami-Dade and Palm Beach counties, forcing the closure of many popular beaches on Thursday and leaving hundreds of dead fish in its wake, according to local reports.

This is the first time in decades the toxic algae has affected both of Florida's coasts at the same time, the
Associated Press reported.

Mom and baby West Indian manatees in Three Sisters Springs, Florida. James R.D. Scott / Getty Images

2018 has not been a good year for Florida's iconic
manatees. A total of 540 sea cows have died in the last eight months, surpassing last year's total of 538 deaths, according to figures posted Monday by Public Employees for Environmental Responsibility (PEER).

The figure will likely climb higher before the year's end amid the state's ongoing
toxic algae crisis. The red tide in the state's southwest is the known or suspected cause of death for 97 manatees as of Aug. 12, the Florida Fish & Wildlife Conservation Commission recently reported.

Editor's note: Two large-scale algae outbreaks in Florida are killing fish and threatening public health. Along the southwest coast, one of the longest-lasting red tide outbreaks in the state's history is affecting more than 100 miles of beaches. Meanwhile, discharges of polluted fresh water from Lake Okeechobee and polluted local runoff water from the St. Lucie and Caloosahatchee watersheds have caused blooms of blue-green algae in downstream estuaries on both coasts. Karl Havens, a professor at the University of Florida and director of the Florida Sea Grant Program, explains what's driving this two-pronged disaster.